Tscherny leaves next month to join political and media strategy firm GPlus Europe as its fourth partner.
The EU is currently looking internally and externally to replace Tscherny.
Fellow competition policy spokeswoman Amelia Torres remains.
Tscherny is bound by certain restrictions for a year after his departure from the EU in order to avoid conflict-of-interest issues.
GPlus managing partner Nigel Gardner said Tscherny will be restricted from working on certain accounts during this period.
He joins in September, leading GPlus's four-strong competition team.
'We're building up a competition practice and Michael will be a major ingredient to that,' said Gardner.